1. in concept formation, the best or average exemplar of a category. For example, the prototypical bird is some kind of mental average of all the different kinds of birds of which a person has knowledge or with which a person has had experience.

2. more generally, an object, event, or person that is held to be typical of a category and comes to represent or stand for that category. See prototype model.

3. an early model of something that represents or demonstrates its final form. —prototypal, prototypical, or prototypic adj.